Spatially resolved in situ analysis of anode and cathode flooding in an industrial-scale PEM fuel cell

Cell flooding is a major challenge limiting the performance and durability of proton exchange membrane fuel cells (PEMFCs). In large - area cells, conventional measurements provide only spatially averaged information, potentially masking localized flooding and degradation. In this study, cathode and anode flooding were investigated using a novel segmented PEMFC capable of providing spatially resolved voltage, impedance, and cyclic voltammetry (CV) measurements. Cathode flooding primarily affected the cathode outlet region and caused mostly reversible performance losses. In contrast, anode flooding induced severe and highly localized degradation near the anode outlet, with voltage losses of up to 170 mV and increased high-frequency resistance (HFR) and mass transport resistance. After recovery, up to 50 mV of the voltage loss remained, and the HFR did not recover, indicating irreversible damage. Spatially resolved CV measurements revealed up to 50% reduction in electrochemically active surface area (ECSA) near the anode outlet, indicating severe catalyst degradation associated with hydrogen starvation and carbon corrosion. SEM showed a reduction of approximately 65% in the cathode catalyst layer thickness, while XRD revealed significant platinum particle growth. These results highlight the importance of mitigating anode flooding and the value of spatially resolved diagnostics for improving PEMFC durability and lifetime.